Ion implant dose control

Details Ion implant dose control Ion implant dose control

2005-03-22

2005-03-22

Nguyen, Kiet T. (Department: 2881)

Radiant energy

Irradiation of objects or material

Irradiation of semiconductor devices

Reexamination Certificate

active

06870170

ABSTRACT:
This invention is concerned with the control of implanting ions into a substrate, such as doping semiconductor wafers. The ion beam is measured to ensure waters are implanted with the correct, uniform ion dose. The incident ion beam comprises ions and neutrals, yet detectors measure only ions. The ions
eutrals ratio varies with the ion implanter's chamber pressure that in turn is known to rise and fall when the ion beam is on and off the wafer respectively, according to a characteristic time constant. This invention provides methods of correcting measured ionic currents to account for neutrals using the time constant. Initially an assumed time constant is used that is later improved by measuring the ionic current after a delay sufficient to allow the chamber pressure to recover to its base value. The time constant may also be improved by removing any quadratic variation in already determined true beam current values.

REFERENCES:
patent: 4234797 (1980-11-01), Ryding
patent: 6297510 (2001-10-01), Farley
patent: 6639231 (2003-10-01), Simmons et al.
J. Kraupner et al., “Dose Theory and Pressure Compensation on Axcelis GSD High Current Implanter” in IEEE in the Proceedings of the 14th International Conference in ION Implantation Technology, pp. 260-263.

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